The length of the jacket varies by size. For the 3XL, at the back from the collar to the hem is 35″ (89cm). For the 8XL, at the back from the collar to the hem is 40″ (101.5cm).

5XL armpit to armpit 34″, sleeve length 22.5″ from underarm to end of cuff, length for jacket 38″ collar to hem at the back
8XL armpit to armpit 41″, sleeve length 22.5″ from underarm to end of cuff, length for jacket 41″ collar to hem at the back